Standard Member

asked dealer what 2 channel amps for sterio only work best with my bw cdm1nts which are rated 50-120 watts, he suggested roksan caspian and a densen amp, the densen is rated at 60w/p/ch, he stated the b&ws draw lots of current from an amp ,its not so much about wattage as current etc, could i have a simple explanation of this or why some amps of might feed (said current) better than others, larger transformers etc????? thank you

Well-known Member

Originally posted by mick23 asked dealer what 2 channel amps for sterio only work best with my bw cdm1nts which are rated 50-120 watts, he suggested roksan caspian and a densen amp, the densen is rated at 60w/p/ch, he stated the b&ws draw lots of current from an amp ,its not so much about wattage as current etc, could i have a simple explanation of this or why some amps of might feed (said current) better than others, larger transformers etc????? thank you

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Mick both amps you mention are fine amps, but the one I would plump for just now (give a demo to at least) at your price range would be the Unison Research Unico Remote £750 which is a 80 watt Valve/Mosfet int. amp draws hefty amounts of current from the mains which means it is not lacking is the supply department for speakers that are a tough load, I would beware of dealer speak about amp power ratings many manufaccers like Naim or NAD have relatively lower powered amps that punch above their weight, very lowish THD ratings are another indicator of an amps stability when supplying current IMHO.

Unico Remote
Unico is a stereo integrated amplifier using both valve and solid-state technology. The combination of pure triode valve input stage and Mosfet output stage gives 80 Watts per channel with the delightful sonic character of a well-designed tube amp. Robustly built and with handsome looks of understated elegance, the Unico is every inch a class product. Complete with radiowave remote control and operated via an attractive handset. Available in both Line and Line + Phono (MC/MM) versions.

Standard Member

to tell you the truth cant really afford any of the above,went into shop to see what might be avaliable to drive cdm1nts and be better than 3802 in sterio, i was hoping a cheaper nad or simular,but it seems by other threads etc,must spend £700+(would not like to guess what a replacement valve if needed might cost thesedays) thanks all

Guest

Sadly, the power "rating" of amplifiers often doesn't really mean that much at all!

Quite often you can get what appear to be modestly rated amps of say 40 or 50W/ch, massively outperforming units rated more than twice as high.
The differences in the way the figures are measured, and what they can hide with those figures is surprising.

Likewise, speaker impedances can be a bit misleading too.
The figure quoted is a nominal figure - the min and max figures would be handy too. A speaker quoted at a nominal 4ohms for instance can easily dip to 2ohms or below, and can peak considerably higher.
2ohms is a very difficult load for many amps, especially budget types. In fact many budget units can struggle with 4 ohms, especially at higher playing levels.

Standard Member

spoke to yet another dealer re cdm1nts and 2 channel for sterio etc naim nait at £750 has av switching but this is only 30watts per channel, could this drive the bw when amp rating is 50-120watts without damaging amp or speakers,getting confusing

If you have a notion for a NAD, have a word with Richersounds.You should get a C350 for £199.99 .Maybe consider one of the NAD power amps as well,or a C370.Any of these options will be well under £700.hth

A stupid man behaves stupidly, not because he wants to, or tries to, or is motivated to, but simply because he is what he is!

Guest

B&W are just being a bit cautious with their ratings - all it means really is that in their opinion, an amp of less than 50W/ch will be unlikely to have the current delivery needed to drive them properly. However, this is really a bit of a gross generalisation.

Many amp manufacturers are very optimistic with their ratings, while others are very conservative. Usually (not always though) the optimism is often at the the lower end of the market, while the conservatism is at the higher end - I guess they feel that the people looking to buy at the higher end, are less likely to be impressed with spec sheet figures.
The ratings are often not measured in the same way in any case - you can "massage" these figures to make your amp seem more powerful than another.
In the US, these games got to the point where they felt they had to legislate on the issue.

You can quote power output with only a single channel driven (this hides deficencies in the power supply), or quote it at a specific frequency such as 1kHz, rather than across the entire 20-20000Hz audio range (some amps may deliver say 100W at 1kHz but can't deliver that much at 50Hz), or quote it into a resistive load (power is at a maximum when the load is purely resistive - speakers aren't), or quote it at differing THD levels (you may get 100W for instance at 1% THD, but only 50W at 0.1%), or not use RMS power ratings (12Vrms for instance is about 34V pk-pk, so you can make the power seem greater -
PMPO has to be the biggest con here - I'm sure we've all seen those active 300W PC speaker for £15 )
There are others too.

Take a an amplifier which can deliver say 8Wrms/channel, full band, at 0.1%THD into 8ohm speakers - doesn't look too good eh - so let's doctor the figures a bit.
Using peak values (and rather conveniently simply forgetting to state this on the spec sheet), into a resistive load (not a reactive one like speakers), at just 1kHz, at a higher THD, say 0.5%, can easily mean you can publish figures of 200W/channel or more - far better for the spec sheet, but a far cry from "reality".
It may sound incredible, but sadly it's true! It also explains why a "true" 50W amp can deliver transient peaks of 300W or more!

OK, most hifi manufcaturers don't push it that far, but they do use a few of these tricks on the spec sheet.

Although I'm not familiar with that particular model, I'd be very surpised if this Naim 30W/ch amp struggled with your speakers!
It may not necessarily sound any better than what you already have though, so a personal demo may be a wise idea if you are considering spending that much.
Have a listen to something like a NAD amplifier from Richer Sounds as well - well known to be very conservatively rated, they can usually drive most 4ohm speakers without problem, so your B&Ws shouldn't be an issue either - usually around £2-300.

Standard Member

see in latest what-hi new nad 3020bee at £220 rated at 50w might demo this when avaliable with cdm1nts and demo side by side with a 3802 to see if there is any differance re 2 channel sterio, do not know wheather nad has any av switch etc which would be handy

Standard Member

nad 540 cd player connected to denon via phono (qed) tried digital coax ,could not tell any differance, speakers still sound what i would describe as "harsh" got them just after queens jubilee, perhaps need a bit more (running in) thanks again

Banned

This output versus speaker thing confuses loads of people. Some Amps can swing large amounts of current. Usually price is a good indicator of amp performance in this arena ( leaving aside valve amps for the moment ). So, if you go down to your nearest comet etc and pick a cheap 30W amp for 100 quid or so , it is unlikely to have the same type of power supply as a 30 Watt Naim. The Naim will have a lot more control of the speakers, particularly with deep base parts of the music as these require large current swings.

So, if you pick up a small battery powered radio with an output of less than 0.5W and feed this into 500Watt speakers at full volume, the amp will clip ( go into distortion ) and after a short time you will probably have blown speakers. On the other hand take an expensive 250Watt amp , such as a Krell and feed it through a pair of 40 Watt speakers, the amp will never distort so the speakers are unlikely to be damaged, unless you drive them at very high volumes ( using them as a PA system in a large hall would do it).

The other thing is speaker efficiency, take a pair of high efficiency horn loaded speakers, drive them with a moderate 10W -15W valve amp and make your ears bleed. On the opposite side a pair of sealed unit 30 Watt low efficiency speakers that are difficult to drive, would give a 30 Watt valve amp a problem or a cheap 30 Watt transistor amp.

Standard Member

thanks guys, yes i think this is what dealer was getting at, densen 60watt amp or rocksan can drive my cdm1nts better than some other brands of maybe higher wattage figures, trouble is all the amps mentioned are £700+ unless i demo them and try for s/hand amps

Banned

My advice, go secondhand. Find a good s/hand specialist who will let you take the amps home to try in your set up. I always bought new until about 8 years ago, once you buy s/hand you loose the depreciation, can afford a better amp for the money and if you do want to upgrade ( or just dont like the sound ) chuck it back in for something else. Seven hundred would buy you an immaculate Naim 72/140 pre power for instance.

Banned

Good tip, but watch out with secondhand buys. Once upon a time, my local dealer asked me round to listen to a Naim amp he was being offered, as it sounded a bit strange. I agreed and on further investigation the internals had been modified to a Hitachi amp and some lead weights.